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ORIGIN AND FORMATION OF PETROLEUM

By Donatien Ishimwe, Junior student in petroleum Chemistry, American University of Nigeria

Relevant articles:

(1) Petroleum Systems and Elements of Petroleum Geology ,

(2) History of World Petroleum Industry : Remarkable Eras of Oil and Gas Industry 

Petroleum is defined as any mixture of hydrocarbons that can be recovered from a drill pipe (Sephton A. & Hazen M, 2013). It occurs in form of oil and gas which mainly have a chemical composition of hydrocarbons of various carbon chains.

Origin

By referring to different grounds from two opposing theoretical hypothesis, petroleum origin and formation still become a polarized topic of scientists’ debates. These theories are abiogenesis and biogenesis. Abiogenesis-inorganic origin of petroleum, is an oldest theory which suggests that petroleum comes from the underneath part of the mantle very long time ago before the existence of life on earth (Mendeleev, 1877). The second hypothesis, biotic or organic origin suggests that petroleum is formed from biological matters, left behind by very ancient lives. These matters become subjected to high temperature under the absence of oxygen. The last hypothesis, biogenesis is currently accepted by many people due to how it is supported by various valid grounds while the first one is more doubtful. Its early supportive tenets lost their truth, especially when they fall in contraction with modern science.

Historical background of petroleum origin hypothesis

The idea concerning the origin of petroleum dates back to the 18th and early part of the 19th century, when the chemical nature of petroleum was not known. Abraham Gottlob Werner and supporters of neptunism in the 18th century considered basaltic sills as solidified oils or bitumen. While these concepts proved not solid, the primary idea of an association between petroleum and magmatism has then persisted as Alexander von Humboldt proposed an inorganic abiogenic hypothesis for petroleum formation after he saw petroleum springs in the Bay of Cumaux (Cumaná) in Venezuela. He is quoted as saying in 1804, "the petroleum is the product of a distillation from great depth and issues from the primitive rocks beneath which the forces of all volcanic action lie". As it is said above other prominent advocate of the abiogenic hypothesis included Mendeleev (1877) and Berthelot (1827-1907). The Soviet Russian geologist Nikolai Alexandrovitch Kudryavtsev also proposed the modern abiotic hypothesis of petroleum in 1950s. On the basis of his analysis of the Athabasca Oil Sands in Alberta, Canada, he concluded by denying the existence of "source rocks" that could form the enormous volume of hydrocarbons, and as consequence he offered abiotic deep petroleum as the most admirable explanation. (Humic coals have since been proposed for the source rocks. Others who continued Kudryavtsev's work are Emmanuil B. Chekaliuk, Petr N. Kropotkin, Georgi E. Boyko Vladimir B. Porfir'ev, , Vladilen A. Krayushkin, , etc,..In 21^st century the most prominent supporter of the hypothesis are Astronomer Thomas G. and Jack Kenney.

Abiogenetic origin of petroleum.

“Early in 16th century, a theory of the origin of oil stated that it resulted from very deep carbon deposits that have been around far longer than life on this planet. That theory, lately became known as the abiotic oil formation (AOF) theory, was largely [ignored]and forgotten until rather recently when a few people-some of them scientists revived it and backed  it with some tenets”.(Petroleum , 2014).

As the earth existence is date back to 4.5 billion years, the Abiotic theory is said to occur in that time, before the appearance of any form of life. The hypothesis bases on the fact that some of harvested hydrocarbons and other associated substances have a very deep origin, indeed they are widely found in the universe. Methane is said to be present in the atmosphere of Jupiter, Saturn, Uranus, on others planets as well as moons and meteorites found in the solar system. Russian chemist and mineralogist Dimitri Mendeleev and scientists of the epoch have had a great influence supporting the hypothesis. “They propose that abiogenic methane reflects a cosmic organic inheritance that is subsequently released by the mantle and migrates towards the surface utilizing weaknesses in the crust such as plate” (Sephton A. & Hazen M, 2013). Recently in 20^th century, members of so called “Russian-Ukrainian School” supported the hypothesis by stating that generated methane polymerizes into higher molecular weight hydrocarbons which results into petroleum deposits, the fact which is also persuade by finding increased abundance of methane gas in the depth of petroleum basin. (Sephton A & Hazen M, 2013).The tenets supporting abiogetic origin of petroleum are in the following way.

1. The existence of methane on other planets of solar system, meteors, moons and comets.
2. The biogenic explanation fails to explain some of hydrocarbon deposit characteristics.
3. The crude oil distribution of metals fits better with upper serpentinized mantle, primitive mantle and chondrite patterns than the oceanic and the continental crust, and never shows any correlation with sea water.
4. The helium and other noble gas association with hydrocarbons.
5. Deep hydrocarbon seeps.
6. Hydrocarbon-rich areas tend to be hydrocarbon-rich at various different levels.
7.   Some proposed mechanisms of abiogenesis formation of petroleum.

Biogenesis.

Biogenetic origin of petroleum (Hydrocarbons) suggests that petroleum come from a long time decaying of died organisms such as planktons, zooplankton ad other form of biological species under a subjection of high temperature. This hypothesis is currently accepted by many people around the world and it has many viable supporting grounds which fits well modern sciences. According to that hypothesis, very long time ago, the organisms (marine living things, terrestrial) died and buried and covered by silt in a sedimentary basin where they undergo a very slow and very long lasting physical and chemical transformation which involves processes such as diagenesis and kerogen formation.

The more conventional view of petroleum formation is that it formed when selected aliquots of biomass from dead organisms were buried in a sedimentary basin and subjected to diagenesis through prolonged exposure to microbial decay followed by increasing temperatures and pressures. Oxygen-poor conditions, produced by exhaustion of local oxygen levels by biomass decay and often sustained by physical barriers to oxygen recharge, are obvious enhancers for fossil organic matter preservation and passage into the geosphere. The major organic components in life are large, high molecular weight entities and the most resistant of these units are preserved in sediments, augmented by cross-linking reactions that polymerize and incorporate smaller units into the complex network. The high molecular weight sedimentary organic matter is termed kerogen from the Greek for “wax former.” It is worth noting that not all of life’s organic matter is reflected in kerogen. Even under relatively favorable conditions less that 1% of the starting organism, representing the most resistant chemical constituents, may be preserved (Demaison and Moore 1980).

The hypothesis of biotic origin of petroleum has many plausible evidences which can indeed allow scientists to simulate the production of petroleum (crude oil). Today advancements in science such as chemistry-knowledge about carbon and its compounds and geology make the hypothesis well understood and well useful. The most plausible evidence is the focus on the stage of what so-called “development of hydrocarbons”, from peat to anthracite and equally from algae to oil.

Different perspectives behind the arguments between petroleum origin hypotheses.

Biotic origin of petroleum inspires the possibility of exhausting oil reserves and abiotic hypothesis assure quasi-unlimited supplies of oil and gas reserves. Therefore many issues regarding energy renewability rises. According to the website Petroleum.co.uk, politics as the main driver of every issue in our modern socio-economic aspects of living, the arguments of abiotic versus biotic origins of petroleum are caused by some hidden reasons which are for particular interests and politically motivated. For example, “a limited supply can be used to control people and as justification for actions like war. An unlimited supply, on the other hand, means that we need not worry about running out, that we ought to be able to drill for more oil and increase the daily supply so as to decrease price, and so forth” ( Petroleum , 2014).

Conclusion

Biotic origin of petroleum fits today science with plausible evidences and it is commonly accepted as the true hypothesis to explain the origin of petroleum regardless of some few confrontations with its counterpart.

REFERENCE

Abiotic oil Formation, Retrieved on 10.09.2014. http://www.petroleum.co.uk/abiotic-oil-formation.

Ballentine CJ, O’Nions RK, Oxburgh ER, Horvath F, Deak J (1991) Rare gas constraints on hydrocarbon accumulation, crustal degassing and groundwater flow in the Pannonian Basin. Earth Planet Sci Lett 105:229-246.

Sephton.A .S & Hazen R.M (2013). On the Origins of Deep Hydrocarbons. Reviews in Mineralogy & Geochemistry.Vol.75[449-465].

Wood BJ, Alison P, Frost DR (1996) Water and carbon in the Earth’s mantle. Philos Trans R Soc London Ser A 354:1495-1511

Wood BJ, Bryndzia LT, Johnson KE (1990) Mantle oxidation state and its relationship to tectonic environment and fluid speciation. Science 248:337-345.